Electronic switch



,Aug. 18, 1959 P. H. WEISS 2,900,504

ELECTRONIC SWITCH Filed June 11, 1956 OUTPUT INVENTOR. P/i/l A! WE/S s ELECTRONIC swrrcn Phil H. Weiss, Los Angeles, Calif., assignor, by 'mesne assignments, to Paramount Pictures Corporation, New York, N.Y., a corporation of New York Application June 11, 1956, Serial No. 590,608

4 Claims. (Cl. 250-27) This invention relates to switches, and, more particularly, to improvements in electron switches.

An electron switch usually consists of at least two tubes, each of which may have a different signal source applied to its input. It is usually desired to switch one or the other of the signals derived from these two sources from a common output point of the two tubes at some desired times. There are a considerable number of circuit variations for performing these operations. Usually, however, these prior-art circuits either introduce switching transients into the signal being switched or distortion thereof, or the switching cannot occur with a suitable rapidity.

It is an object of this invention, however, to provide an electron switch wherein there are no switching transients found in the output.

It is another object of the present invention to provide an electron switch which may be direct coupled between the signal input and the output.

It is still another object of the present invention to provide a novel, useful, and simple electron switch circuit which does not distort the signal being switched.

These and other objects of the invention are achieved by providing two pairs of electron discharge tubes, each of which has its anodes connected to a common source of B+. The cathodes of each pair of tubes are connected together and then, through a separate diode, to a common output point. A separate cathode load impedance, such as a resistor, is provided for each of the common cathodes. The common output point is biased to a posi tive voltage value. One control grid of each of the pairs of tubes, which is designated as the input control grid, is biased to the same voltage potential. One of the other control grids of one of the pairs is biased to a positive potential below that applied to the input control grid. The other control grid of the other of the pairs is biased to a positive potential which is above that of the bias on the input control grid. In order to switch the signals received at the output from one to the other of the two input control grids, the values of the voltages biasing the second of the control grids in the pairs of tubes are interchanged.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing, which is a circuit diagram of the embodiment of the invention.

A circuit diagram of an embodiment of the invention is shown in the drawing. It comprises a first vacuum tube 10, having anode 12, control grid 14, and cathode 16, and a second vacuum tube 20 paired therewith, having anode 22, control grid 24, and cathode 26. The anodes 12, 22 are connected together to a source of B+ potential. The cathodes 16, 26 are connected together and have a common bias resistor 30 and are connected nited States Patent through a diode 32 to a common output point or terminal 34. A second pair of tubes 40, 50 each also has an anode 42, 52, a control grid 44, 54, and a cathode 46, 56. The anodes 42, 52, are connected together to a common B+ source. The cathodes 46, 56 are connected together and to a cathode bias resistor 48 and, also, through a diode 50 to the common output terminal 34. The common output terminal is biased from a voltage source through a biasing resistor 60. It should be noted here that the values of the resistors, condensers, and biasing voltages which are shown in the circuit diagram, are shown by way of example of an operative embodiment of the invention and are not to be construed as a limitation.

One of the control grids of each one of the pairs of tubes 14, 54 is to be considered as the input control grid for signals from two difierent signal-input sources. The other of the control grids can be considered as switch control grids in the sense that signals to control the switching of the electron switch are applied to these control grids. The signal-input control grids are both biased from voltage sources at substantially the same values. The bias is applied through two isolating resistors 62, 34. A bias is also applied from two voltage sources to the two switching control grids, one of which is lower than the other. For example, the bias applied to the grid 24 has a value of 68 volts and the bias applied to the grid 44 has a value of 92 volts. Electron switch control is efiectuated by interchanging the value of the bias voltages applied to these switching control grids.

Examining the condition of the circuit when the static voltages shown in the drawing are applied, it may be seen that the condition at the common cathodes of tubes 10 and 20 is that the tube 20 having the 68-volt control grid bias applied is cut oil because of the presence of an volt bias applied to the tube 10 control grid. This effectively raises up the cathode bias, which cuts oif the tube 20. Thus, signals applied to the input control grid 14 can be transmitted through the tube 10 to the output terminal 34. Examining the condition of the other pair of tubes, the tube 40 having a 92-volt bias applied to its switching control grid cuts 01f the input tube 50 having the 80-volt bias applied to its input control grid. Thus, signals applied to the control grid 54 are not translated to its cathode. As a further block to any signals coming through from the second pair of tubes 40, 50, the DC. level at the terminal 34 as a result of the bias applied is substantially 80 volts. Thus, since the anode of the diode 5 1 is at a lower potential than its cathode, no signals can get through. However, the anode of diode 32 is higher than its cathode and signals can be translated thereby.

In order to reverse conditions of signal translation between the input control grids and the common output terminal 34, a 68-volt bias should be applied to the input of tube 40 instead of 92 volts, while the bias applied to the grid of tube 20 should be raised to 92 volts instead of 68 volts.

As described above, switching of the embodiment of the invention is achieved by interchanging the bias voltages being applied to the grids of the switching control tubes. For a rapid switching operation this result may be achieved by simultaneously applying positive and relatively negative pulses to the switching input terminals 80, 82. These have the effect of substantially establishing the required potentials at the switching control grids, wherein the switching between the two inputs and the output is controlled. A suitable circuit for accomplishing such switching may be the well-known univibrator, which is a two-tube astable circuit, or the well-known multivibrator or two-tube bistable state circuit. The required out-of-phase outputs are obtained from the two anodes of these two-tube circuits which are coupled to the terminals 80, 82. The two-signal source switching is then controlled by the application of pulses to the flip-flop or univibrator circuit input. This, in turn, enables one or the other of the signal-input tubes to translate the signal to the output; I

In order to convert the embodiment of the invention into a direct-coupled system, it is merely necessary to eliminate the input coupling condensers70, 72 and apply the input signals through the isolating resistors 74-, 76. No other changes in the circuit need be made. The circuit may be used to switch either input to the output at an extremely rapid rate without introducing switching transientsor other distortion into the output.

Accordingly, there has been shown and described above a novel, useful, and improved electron switch which eliminates switching transients from the output and permits the use of direct coupling between the input signal sources and the output whereby direct current level changes may be avoided.

I claim:

1. An electronic switch for selectively switching two signal sources to a common output comprising a first pair of electron discharge tubes, a second pair of electron discharge tubes each having an anode, cathode, and control grid, a pair of cathode load impedances, the cathodes of said first pair of tubes being connected to one of said cathode load impedances, the cathodes of the second pair of tubes being connected to the other of said cathode load impedances, an output terminal, a separate rectifier means coupled between said output terminal and each of said cathode load impedances, means to bias the tubes of said first pair of tubes to block them for the translation of signals applied to the control grid of one of them, means to bias the tubes of said second pair of tubes to enable the translation of signals applied to the control grid of one of them, and means to apply a bias to said rectifier means to enable the conduction only of the one coupled to said second pair of tubes.

2. An electronic switch for selectively switching two signal sources to a common output comprising first and second pairs of electron discharge tubes, one tube of each pair being a signal input and the other being a switching control tube, each of said tubes having an anode, cathode, and control grid, a first cathode load resistor, a second cathode load resistor, means coupling the cathodes of said first pair of tubes to said first cathode load resistor, means coupling the cathodes of said second pair of tubes to said second cathode load resistor, an output terminal, a first diode coupled between the cathodes of said first pair of tubes and said output terminaL- a second diode coupled between the cathodes of said second pair of tubes and said output terminal, means for selectively biasing the control grids of said switching control tubes to block one of said signal input tubes for the translation of signals and to permit the other switching control tube to be blocked by said other signal input tube, and means to apply a bias to said diodes having a value to enable the conductionof only the one of said diodes connected to the pair of tubes in which the signal input tube is not blocked.- Y

- 3. An electronic switch for selectively switching two signal sources-to a common output comprising a first and second pair of electron discharge tubes one tube of each pair being a signal input tube and the other being a switching control tube, each of said tubes having an anode, cathode, and control grid, first and second cathode load resistors, means for connecting the cathodes of said first pair of tubes to said first cathode load resistor, means for connecting the cathodes of said second pair of tubes to said second cathode load resistor, first and second diodes, an output terminal, means for respectively connecting said first and second diodes between the cathodes of said first pair of tubes andsaid output terminal and the cathodes of said second pair of tubes and said output terminal, means for applying separately a first bias to each of the control grids of said signal-input tubes and to said output terminal having substantially the same value, and means for selectively applying a second bias to the control grid of one of said switching control tubes and a third bias to the control grid of the other of said switching control tubes said second bias being less than said first bias and said third bias being greater than said first bias whereby the signals appearing at said output terminal are those corresponding to the signals applied to the signal-input grid of the pair of tubes in which a second bias is applied to the grid of the switching control tube. 4. An electronic switch as recited in claim 3 wherein said first and second diodes each have an anode and cathode and are connected with their anodes to said output terminal and their cathodes to the respective cathodes of said first and second pairs of tubes.

References Cited in the file of this patent i UNITED STATES PATENTS 2,538,028 Mozley June 24, 1947 2,572,792 White Oct. 23, 1951 2,781,448 Struven Feb. 12, 1957 FOREIGN PATENTS 630,123 Great Britain Oct. 5, 1949 

